Printing on post cards, greeting cards, etc. amounting to several hundreds 100 sheets has recently been conducted by a handy printer using an orginal plate prepared from a heat-sensitive stencil sheet comprising a porous sheet and a thermoplastic resin film (hereinafter referred to as mimeographic printing). Original plates which can be used in this printing system have conventionally been prepared by a process in which a heat-sensitive stencil sheet is superposed on an original prepared by printing a layout by a word processor or by reproducing a layout by plain paper copying (PPC), and the stencil sheet is then exposed to a flash by means of a flash bulb, etc. Alternatively, a layout may be directly printed on each card by means of a word processor. However, any of these techniques is not only troublesome and time-consuming but incurs cost.
In the light of these circumstances, the inventors previously proposed an original plate which can be perforated directly by means of plate making using a thermal head, such as a word processor. The original plate used in this system comprises an ordinary stencil sheet on one side of which reinforcing paper is adhered, and the area of the reinforcing paper corresponding to a printed image is cut out. Therefore, image perforation using a thermal head is easy, and mimeographic printing can easily be carried out simply by cutting off the part corresponding to a printed image.
However, since the stencil sheet itself has a conventional construction, it was difficult to clearly distinguish a perforated area using a thermal head from a non-perforated area. Therefore, workability in ink application on the perforated area before conducting handy printing was poor, particularly in multi-color printing in which two or more kinds of inks different in color are applied to different areas of a single original plate.
In more detail, in the stencil sheet having been partly perforated by thermal printing with a thermal head to form an image, the perforated area and the non-perforated area cannot be clearly distinguished with eyes due to a small contrast therebetween. On the other hand, where multi-color printing is conducted using a single original plate, inks having different colors should be separately supplied to the original plate in different places of the perforated image before mimeographic printing. As set forth above, since the perforated part of the conventional heat-sensitive stencil sheet is not clearly distinguishable, it has been difficult to apply each of inks having different colors on a single original plate according to different colors of a desired image with good workability and high efficiency.